A gate driver is a power amplifier that accepts a low-power input from a controller IC and produces a high-current drive input for the gate of a high-power transistor such as an Insulated Gate Bipolar Transistor (IGBT) or power metal-oxide-semiconductor field-effect transistor (MOSFET). A gate driver typically includes a level shifter circuit in combination with an amplifier. A level shifter is an electrical component that converts digital signals from a low-side voltage domain to into a high-side voltage domain. The input signals are provided in reference to the low-side domain, while the output signals provided in reference to the high-side domain. Both the low-side and high-side are separate and electrically isolated from each other.
Gate drivers are typically used to drive inductive loads. For example, a motor bridge driver can be used to drive H-bridge or three-phase brushless direct current (DC) motors. One issue with current-controlled high-side gate drivers is that, in a motor driver application, the output current of the gate driver may be sensitive to rapidly changing common mode voltage transients. This sensitivity is caused by parasitic capacitance, especially the gate-drain capacitance of the driver's output transistors. Because of current consumption and settling time limitations, a typical current-controlled gate driver circuit cannot maintain a constant output current during a short common mode voltage rise time (e.g. 50 ns). As a result, a current dip (or at least a current reduction) occurs during the rising edge of the common mode voltage.